Hypothermia, which comprises a body temperature of 95° F. or below, is a serious condition for which all trauma patients are at risk. Due to the use of anesthetics and the administration of cold intravenous fluids, 65% of all surgical patients experience hypothermia. Hypothermia causes discomfort and can cause potentially life-threatening complications, such as ventricular fibrillation, especially during surgery.
In an operating room setting, fluid may be provided to a trauma patent at flow rates varying from 20 ml per minute to 1 liter per minute. Fluid to be provided intravenously flows through a plastic tube extending from a fluid reservoir (such an intravenous bag) to a vein within the patient. The intravenous bag is typically stored or held in the operating room, and when administered to the patient, it is administered through a tube which may be 6 to 8 feet long. Operating rooms are usually maintained at about 55° F. to about 65° F. degrees, and, consequently, any fluid in the intravenous bag is often cooled to the ambient temperature which is well below body temperature. Infusing this cold fluid intravenously into the already stressed surgical patient can significantly affect the patient's body temperature and greatly increase the chances that the patient will experience hypothermia and other serious complications.
Hypothermia and other deleterious effects of cold IV fluids can be avoided by heating the IV fluid. However, even with the current, overwhelming evidence of the clinical benefits of fluid warming (which includes avoidance of hypothermia, discomfort, shivering, and reduced infection rates, faster healing, shortened hospital stays, and reduced risk of serious heart injury), only about 4% of the 45 million U.S. hospital infusions were warmed during the year 2000. Almost none of the 4 million emergency infusions were warmed. Thus, a simple, cost effective device is needed to warm fluids provided intravenously to patients.
Heating may be accomplished prior to use, but this may be impractical in an emergency settings or field applications. Thus, heating may be advantageously accomplished during the administration of the intravenous fluid, through heat exchange between the intravenous fluid and a heat source placed in the intravenous flow path. Several devices have been proposed for use in warming intravenous fluid. Kistner, Intravenous Warming System, U.S. Pat. No. 6,139,528 (Oct. 31, 200) discloses an electrical heating system, where intravenous fluid passes through a heat exchanger and is heated by electrical heating elements. White, Apparatus and Method for Warming Intravenous Equipment, U.S. Pat. No. 4,934,336 (Jun. 19, 1990) discloses a system in which flexible containers holding crystalizable supercooled aqueous salt solution are packed around an IV bag and the proximal extent of the IV tube.